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E. REISZ.

DUPLEX CONNECTION FOR TELEPHONE RELAYS.

APPLICATION HLED HJLY3I. 1915.

Patented N0v. 18, 1919..

2 SHEETS-SHEET I.

A i e? a BEISZ. DUPLEX CONNECTION FOR TELEPHONE RELAYS.

APPLICATHIIN FILED JULY31.?9I5

- Patented Nov. 18, 1919.

2 SHEETS-SHEET 2- -ZEzvazz Z29 zggerz Rewz UNITED sTATns rgrnu'r OFFICE.

EUGEN REISZ, OF TREPTOW, NEAR BERLIN, GERMANY.

DUPLEX CONNECTION FOB- TELEPHONE-RELAYS.

Application filed July 31, 1915.

To all whom it may concern:

Be it known that I, Enos: Balsa, a subject of the Emperor of Austria, residing at 'lreptow, near Berlin, Germany, have invented certain new and useful Improvements in Duplex Connections forTelephone- Relays. of which the following is a specification.

1n duplex connections 1 for telephonic trunk line ctn-respondeuce in which the transmission is effected through telephonic relays, there must exist, as is well known, to intensify the incoming currents, some ind l ictive or ot her connection hetweenhotli sides of the trunk and both the primary and the secondary circuits of the relay or'rclays, to allow, of immediate intensification of the transmitter and receiver currents at both sides. In such a. connection, however, the magnified currents are apt to react on the relay and to cause the formation of a current therein, which would render the same inoperative, while. on the other hand, the difl'ercnces in the electric properties of the two sides of the trunks, and which are fre- .quently large, would likewise. have a disturbing etl'ect on the relay action.

In connections of the kind mentioned, such as hitherto used or proposed, the lastmeutioned disturbances of the relay action have been overcome. more or less elliciently by the insertion of so-called artificial lilies, reprodueing as far as possible the electric conditions prevailing in the physical lines, while the lirstanentioned difficulties were obviated by the arrangement of duplicated coils, passed in series only by the line currents, hut traversed in the opposite direction by the magnified relay currents, so as to avoid any action of the same ou' the circuit allotted therewith in the latter case. lioth 'methods have also been combined, by connecting one of the said duplicated coils with the physical, and the other with the artificial line. Such constructions, however. possess practical ditliculties when in use, resulting from the needless consumption of nearly one-half of the electrical energy in the artificial lines, and from the indispensable constant adjustment of the Specification of Letters Patent.

Patented Nov. 18, 1919.

SeriaI No. 43,016.

same to comply with the constant variation of capacity and resistance, almost continually occurring in a trunk line, with the varying value of insulation, leakage losses, etc.

It is the object of this invention to overcome the above-mentioned difiiculties and to obtain a reproduction undisturbed either by the magnified currents or by the different electric properties of the trunk lines on both sides of a relay, Without introduction of artificial lines and the drawbacks caused by them.

For this purpose, each trunk running into the exchange, containing the relay or relays, has a separate trunk section in the vicinity of the relay, coupled with the relay circuits on the one side and with the re mainder of the trunk on the other side, preferably hy the well-known repeater coils. The said section is provided with a third conductor in parallel with the two line wires of the trunk which branches off at the relay side from the exact middle of the repeater coil, in connection with the primary circuit of a relay, and at the other side from the repeater coil in connection with the remainder of the trunk. By these means the two lines constituting one trunk form part of two parallel circuits having a common return conductor, which may be the earth or some separate line =or wire, or an existing telegraph or telephone line as the case may be. liloreover, such a section must have a definite length, so that its damping exponent is above a certain value.

I have found that the influence of the inequalities iu the electric properties of the trunks upon the relay decreases in proportion as the distance of the sources of said inequalities increases. and if said damping exponent is properly chosen, which means that it may be chosen above a. certain value depending upon the length of the trunks, then these inequalities will be of no consequence. The third conductor will allow a connection that excludes every influence of the magnifying currents upon the relay and, at the same time, the high 'alue of the damping exponent will also prevent the inequalities due to the symmetrical connection of the third conductor with respect to the repeater coils, or to unequal electric properties in the two branches of said section, to have any marked influence upon the exact compensation caused by subdividing the repeater coil, which is connected with the primary of the relay, into two absolutely equal parts. These unequal parts or elements which may be present in the circuit are, for example, the one-sided connection of the third eonduetor (the earth), or other electrical differences, even though slight, in the two conductors of the double line such as are made noticeable in long distance lines due to shunts, differences in insulation, andi other causes. It is also to he considered that only a correspondingly large part of the long-distance lines connected to both sides of the relay can he of injurious e'll'ect'on the relay.

I have discovered that. as the distance from the relay iurreases, difl'erences in the characteristics and apparent resistances in the long distance line act injuriously on the relay with diminishing influence. As a result of this discovery, the connection of the third conductor (the earth) as a return line for the intensified currents is not necessarily located at the two end stations themselves but may he located at, a predetermined distanee from the relay dependent on its sensitireness and intensification, and by using indurtion coiln or transformers, the other two parts of the line to which the telephone devices themselves are connected are pure long distance iincs and exclusively double lines. Experience has demonstrated that, even with highly he'nsiti-ve gas-discharge relays, the distance between them and the transformers with the ground plates, at. which normal long distance lines may be connected without all'ecting injuriously the operation of the relay, may be. for example, 200 kilometers where a l millimeter tree line is used, this being sutlicient to prevent reduction of the sensilivenrss ot' the relay.

In such a system it moreover, possible to connect the repeater coil, in connection with the secondary f the relay. into said third conductor. preferably near the point where the same is branched oti from the middle of the repeater roll in connection with the primary relay circuit, wherclrv all the ahore-un'nlioued advantages will also he eecured. sinre the translation of the magnitied currents. as also any rem-lion ol' the same upon the relay will be prevented.

If a plurality of relays (especially two relays. one for each direction) he used. the connection is based (nu-Hy upon the same principle, the dill'rrrnciresiding only in the f t-l that the coil at the end of the section is in inductive or other connection with the primary circuit of a relay that transmits eX- the repeater coil. in the third conductor of said section is in inductive or other relation with the secondary circuit of a relay, the primary of which is in connection with the repeater coil at the end of the other side of the trunk.

In the accompanying illustrative drawings Figure 1 represents a diagram showing the connection according to this invention:

Fig. :2 represents a modification for twb distinct relays;

Fig. 3 shows a modification of the arrangement according to Fig. 2 with a. metallic return conductor;

Fig. t represents a second modification of the arrangement according to Fig. 2. and

Fig. 5 a third modification thereof.

Referring to these drawings:

In the diagram according to Fig. 1 translators l, 2 and i2, 13 are connected into the two trunk lines F, and F representing any kind of two wire lines. The line currents, which are to be reinforced by the relay, act by means of the windings 1i. 4 and 8, 9 upon the winding 5 which is connected into the primary circuit 1 of the relay. The windings T and 11 are connected into the secondary circuit S, that is to say into the, circuit containing: the currents reinforced by the relay.

The currents flowing into the said windings 7 and 11 serve to induce currents contained in the windings 6 and 10, the said currents flowing across the \\ll1(llll!:-. 3. l

and 8, 9 to the translator coils 2 and 12. while the return to the windings 6 and 10 is cti'ected by aid of a third conductor, r. (a, the earth. according to Fig. 1. Provided the damping factor of the portions of the line located between the places where the translators l, 2 and 12. 13 are erected and the place where the relay is situated he snlliciently large. then the currents flowing in the windings 3. 4 and S, 9 will prove to be equal for all practical purposes, so that no reaction on the primary circuit of the relay will occur.

By damping factor is meant. that exponent as a natural logarithm (1/ which. in telephone lines, shows how great is the. decrease in intensity of the voice current in consequence of self-iiulurtion. capa ity. olnnic resistance and other influences. and which apparent resistance" arts to reduce the, intensity of sound in telephone conversations as the distance ot' the telephone increases on a logaritlnnic exponential scale.

It, for exau'iple, the current reinforced by the relay attains the tenl'old value of the original (urnnt, then the damping exponent of each portion of the line situated between the relay and the translators 1, 2 and 3, 4 must be greater than 1. In other words, with rela vs which are so sensitive that they intenslt'y the original speaking current ten-fold, it has been found neces sary to select a distanee between the grounded transformer coils 1--2 and 12-l3 aml the approximately eentrally located relay station which will be sullieient that eat'h of these eondnetor portions shows a weakening in current so that [51:1, eorrespomling to about 200 kilometers oi open double line of 4 millln'ieter copper wire.

.The three wire line portion at both sides of the relay must aeeordingly possess rertain definite value of damping dependent.

upon the degree of reinforcement of the relay, while the impedances of the. three wire portion of the line may be chosen irulepend ently of one another at both sides of the relay.

It will thus be understood that the possibility is given of connecting the one side of the relay to overhead lines and the other side to cable lines without rendering ma-essaev the introdnetion artitit-ially of the m-et-ssarv alue of damping. In this latter ease however these lines must be t't)|1. ll'llt'l( tl up to a ('ertain damping factor. as three wire lines.

In order to explain more t'ull the main advantage of the invention, aml whieh eonin the tart that the whole line is not subject to a eoml'ilirat'ed modification throughout its whole. length or entirely modified by the provision of additional ar rangements or apparatus on at-t'ount of the reinforcement by a relay. hutin its main parts is arranged like any normal trunlt 'line, without s 'ieeial reint'on-ement appliances, the terms damping exponent and cliaraeteristie will hereafter be discussed, and'detlnite examples. with definite values in nnml'iers, will be given.

In every trunk or long distanee line on the one hand, owing to the varying rut-rents,

the eleetrie and magnetic lields t'olnpensnte eaeh other. while. on the other hand. the useful power is transmitted to the other end of the line. The current impulse sent over the line, has to supply the useful power at the other end of the line, as also the power necessarily spent in eonsequem'e of losses oeeurring during the transmission over the line. 'lliesr. losses maybe. restl'it'tetl lult cannot 'be obviated altogether by lIIeimhu-tam'e distributed all over the line. At eat-h point; some it the power transmitted is lost, so that the amount. of powearriving at the receiving end is obviously nun-h smaller than that put in at the transmitting end. lhis law, of t'ourse, equally applies to every ronduetor l'or ('ontinuous eurl'ent. lint the ease of continuous eurrent is a somewhat ditl'erent one. as in the rondnetion of undulating or wave currents the power supplied at one end has notonly to make up for the losses eaused by the resistance and the heating ot' the rondnetor, but also for the losses oreurring: by the transformation of the tltt'll'lt enertrv in the distant parts of the line. The eonsnmption ol eleetrie power in telephone trunk lines is, therefore, governed by another law than the eons-u|np tion in other lines. amt the voltage and eurrent strength (and thereby also the rollsnmption of eleetrie power) deerease aeenrding to an exponential curve. Assuming a wave to have traveled a ('ertain distanee along the line, the current strength will have decreased at Jo at the beginning to at the end of said distance, a in this ease indirating: a number larger than 1 (one). At the end of a distance twieeas long. the current strength of the wave will only possess a J o value equal to Assuming a to have been 2 so tllUHt'll that it has rel'vrenee to 1 (one) km.. (equivalent to unit of length). the intensity of the enrrent in3.1-.lineot/lnn. will v. 0 have been redueed to Now this rednea" tion is termed spare damping the eurrent intensity. The same law holds true with regard to the tension.

The theoretieal dmelrqnneut of the problem gives the same. result. however, in a different form, there being introdueeil in the place of the value a. a value of the same physical quality a (e 2.718 being the basis of the natural logarithms), so that a =e and it is this latter mathematieal expression for the damping 'lllt'll is rommonly used.

The relation existimg between the two statements is the obvious and well-known one that 2.3 log as. The ratios of rur rent intensities or tensions at the ineoming and outgoing ends of a line seetion of 1 km. at the other end being 1+Bzl (B'imlirating a. delinite but very small number). then, in that. ease. q=l+ and, therefore, (522.3 log (1+6). However. for the 8 values which ]n'aetieally arise. the term 3.3 log' (1+3) proves to be approximately equal to '6 fig: 2.3log(] +0050) =2.3'0.0212=-0.0487. Now seeing that B and 8 are almost equal. it follows that on a line having a eonstant [5, the rurrent intensity or tension at. one end of a line 1 km. in length. will bear a ratio to the rurrent intensity at the other end of the line equal to 1+8: l. The value [5 may be termed the spare damping eoetlieient, and (5' constitutes the damping exponent or damping roelliri'eut. for a line 1 km. in length. For all praetieal purposes. the indications aerording to the values B are more easy, the numbers being smaller.

In Fig. 2 of the accompanying drawings there is represented a diagram showing the connections for two distinct, relays for the currents arriving from the two sides of the line.

P and S, indicate the terminals leading to the primary and the secondary circuits, respectively, of the first. relay, whereas I and 5. represent the terminals for the corresponding circuits of the. second relay.

The operation of this arrangement is as follows:

The currents coming from the trunk line F, act by means of the windings 1, 2. and 3, 4 and 5 upon the primary circuit P, of the first relay. The currents reinforced by this relay and coming from the secondary terminals S, are transmitted by the windings 10, 11 and further by the windings 12. 13 to the trunk line l The currents coming from the trunk line l*. a t by means of the windings 13, 12 and S. t) and 5 on the primary circuit l of the second relay and the currents reinforctal by this latter are trans mittcd by the windings T. o and further by the windings '2, l, to the trunk line F In the cas of this arrangement the currents are transmitted in a reinforced state from the one trunk line to the other without giving rise toany reflection.

The degree of reintorccment obtained by means of the arrangement according to Fig. 2 is'consequently much greater than that. obtained by means of the arrangement shown in Fig. 1, since in this latter case the currents, coming from one trunk line are transmitted to the other trunk line by means of the relays, are reflected to an increased degree along the line after passing the transmitting station, this reflection entailing a reduction in the degree of reinforcement.

The arrangement shown in Fig. 3 is identical to that represented in Fig. 3 with the sole, diltercnce that instead of the earth there is employed a metallic return conductor, say for example telegraph lines F and F respectively, running alongside of the trunk lines.

In Fig. 4 there is shown an arrangement in the case of which neighboringtelephone lines are made use of for the purpose of effecting the return of the currents reinforced by the relay. Between the said telephone lines F. and F of the type commonly in use and which run alongside of the lines and: F there are interconnected the bridge coils I), to D The coils D and I1, are located as closely as possible to the place where the relay is situated, while the coils l) and I) are situated as nea as possible to the place where the translator coils 1, 2 and l2. 13 are connected into the circuit.

The currents reinforced by the relay and which are transmitted in the manner above set forth to the trunk lines F and F 2 have no influence whatsoever upon the lines F, and F for the simple reason that the speaking'currcnts do not give rise to any dilferenco in voltage between the two conductors F and F In the arrangement according to Fig. 5 there are connected into two pairs of wire, lines I" to ,I two relays, one for pair provided with the primary circuits I? to 1 and the secondary circuits S to S In addition hereto there are arranged ei ht bridge coils D to I) In the case of 565 said arrangenu-nt no such auxiliary lines are required as are mentioned with reference to the arrangements according to Figs. 1 to 4.

The two strands of a two wireline constitute the return conductors for the reinforced currents of the other two wire line in every direction.

The manner in which this arrangement is intended to operate is the same as that according to Fig. l. y

The places where the coils 1, 2 and 12, 13 are connected into the circuit must be at such a distance from the relay, or the relays, as to prevent any further influencing of the. )artial' current in the windings 3, 4- and 8, 9 in consequence of a connection having been established with the. trunk lines F and F, This will render it impossible for the coils 1, 2 and 12, 13 to be connected into the circuit at the exchange where relays, are located.

The interconnection of artificial lines between the coils l, 2 3, i 8, 9 and 12, 13 (by whichme-ans' the possibility would be 'ven of efl'ectin the connection into the circuit at. the. exchange) does notappear to be Bldrantageous, since thiswould be attended by a considerable reduction of the degree of reinforcement of the relay.

hat I claim is:

1. In combination with a tele hone repeater system comprising double line trunks and a telephone relay between said trunks having a primary and a secondary circuit, a separate trunk section at each side of the relay electrically coupled with the reaminthe relay, or the tWO each der of the trunk and with the relay circuits,

maiuder of the trunk and with the relay.

circuits, and. a third conductor in said section in parallel to the trunk lines of the same branched off from the exact middle of the repeater coil at the relay side and from some point of the repeater coil at the oppo' site side so as to transform said section into two parallel circuits including the two lines of the trunk and having a common return conductor, the said section having a definite minimum length corresponding to a damp-' ing exponent of sufficient magnil ode to prac tically annihilate the effects of the inequalities in the electric properties of the two circuits connected in parallel.

3. In a telephone repeater system com prising a double line trunk and a telephone rclay between said trunks having a primary exciting and a secondary transmitting circuit, the combination of a separate trunk section at each side of the relay provided with repeater coils. one of said coils oupling said section with the remainder of the trunk and another coupling the same with the primary circuit of the relay, and a third con ductor in s'aid section in parallel with the two trunk lines branched oil' from the exact middle of the repeater coil coupled with the primary relay cir'uits and from some point of the r-peatcr coil coupled with the remainder of the trunk, the repeater coil in inductive relation with the secondary circuit he ing arranged in said third conductor near the branching point at the relay side of said third conductor.

4. In a telephone repeater system having double trunk lines and a relay connected with each of said trunk lines to transmit the telephonic conversation from one trunk line to the other, each of said relays having an exciting primary circuit and a transmitting secondary circuit. the combination of separate trunk line so io s at each side of the relay provided with repeater coils, one of said repeater coils being in inductive relation with a corresponding coil at the end of the remainder of the trunk, another coil being coupled with the primary circuit of the relay, the secondary circuit of which is coupled With the other trunk line, a third conductor in said section branched off from the middle of the last-mentioned coil and from the end of the first-mentioned repeater coil at the off side of the section, thus transforming said section into two parallel circuits having a common return conductor, and a third repeater coil inserted in said additional conductor of the section, said coil being in inductive relation with the sec ondary circuit of the relay, the primary of which is coupled with the repeater coil of the other trunk, the separate sections of the trunk adjacent the relays being of such length that their damping exponent is of sufiicient magnitude to overcome the effects due to difference in the electric qualities of the trunks or of the parallel circuits in each section so as to obtain a practically equal flow of current in the two parts ofeach repeater coil coupled with the primary of the associated relay.

5. In a telephone repeater system having double trunk lines and a relay connected with each of said trunk lines to transmit the telephonic conversation from one trunk line to the other, each of said relays having an exciting primary circuit and a transmitting secondary circuit, the combination of separate trunk line sections at each side of the relay provided with repeater coils, one of said repeater coils being in inductive relation with a corresponding coil at the end of the remainder of the trunk and with the relay circuits, a double trunk line running for the extent of said section in parallel with the other trunk lines, and means to connect said second trunk line with the exact middle of the repeater coil at the relay side of the section and with the end of the repeater coil at the opposite side so as to transform the same into a third return conductor connected in parallel with. the two lines of the trunk section, the said section having a definite length corresponding to a damping exponent of suflicient magnitude to practically annihilate the effects due to dificrcnccin the electric qualities of the trunks or ot'the parallel circuits formed in each section by the interposition of the return conductor.

6. In a telephone repeater system lmving ,double trunk lines, a relay connected with each of said trunk lines to transmit the telephonic conversation from one trunk line to the other, each of said rilays having an exciting primary circuit and transmitting secondary circuit, the combination of separate trunk line sections at each side of the relay provided with repeater coils, one of said repeater coils being in inductive relation with a corresponding coil at the end of the remainder ol the trunk and with the relay circuits, at double trunk line running for the extent of said section in parallel with the other trunk lines, and bridging resistance coils in said second trunk line, one of said coils being situated as near as possi ble to the repeater coil connected with the primary relay circuit, the other coil being situated as near as possible to the repeater coil at the offside of the section, the first bridging coil having its middle connected with the exact middle oi? the repeater coil at the relay side, the other lnridging coil having its middle connected to the end of the repeater coil at the distant side of the section, both of the second trunk lines thus forming a third conductor in said trunk section, transfrn'ming the same into two paral lel circuits having a common return conductor, the separate ,trunk line section having a definite length corresponding to a my hand in presence of two subscribing wit- (lnmpmg exponent 0t sufiiclent. nmgmtnde nesses. to pmctnrally anmlulute the effects dueto differences in the electric qualities of the LUGLN trunks 01- of the parallel circuits formed VltllGSSGS-I in each section. ANNEMARIE REIsz,

In testimony whereof I have hereunto set HENRY HASPER. 

